Rulebook 1.6.3: "If the ally gains life in excess of his capacity, it doesn't drain off,"

and

Rulebook 1.6.1.3: "Only a minion who meets the requirements given on a minion card can play it" + Rulebook 1.6.3: "In many cases, a minion card will have a Discipline symbol, a clan symbol and/or a blood cost; in these cases, the card can only be played by a vampire who meets the requirements."
The Nephandus is not a vampire of clan !Tremere, therefore it can't recruit a Nephandus.